Cooper Bussmann ECNR50 Fuse

The Cooper Bussmann ECNR50 is a heavy-duty Class RK5 dual-element fuse designed for high-performance circuit protection in demanding HVACR environments. This 50-amp, 250V time-delay cartridge fuse is specifically engineered to handle the inductive loads of compressors and motors, providing a 10-second minimum time lag at 500% of the rated current. This dual-element construction effectively prevents nuisance blowing caused by temporary motor starting currents or harmless surges while maintaining a secondary element for rapid short-circuit protection up to 200,000 RMS symmetrical amperes. For those in the field, sizing this Bussmann Fusetron at approximately 125% of the motor's full-load amperes (FLA) ensures robust motor overload protection against burnout and single-phasing. The ECNR50 operates at lower temperatures than standard one-time fuses, reducing thermal stress on switches and panels. Its rejection-type design ensures safety by preventing the installation of fuses with lower interrupting ratings in Class R fuse blocks. With a standard 3-inch length and 13/16-inch diameter, it serves as a direct, high-reliability upgrade for existing power distribution mains and branch circuits.

• Dual-element technology provides superior overload and cycling capabilities for heavy-duty HVAC motors.
• Long time-delay characteristic eliminates downtime from nuisance trips during compressor startup.
• Increased safety via 200kA interrupting rating, significantly higher than standard Class K fuses.
• Cooler operation minimizes heat damage to lugs and internal panel components.
• Rejection-style tips prevent improper fuse substitution in critical safety applications.

Can I use an ECNR50 to replace a standard 50-amp non-time-delay fuse?
Yes, as long as the voltage and physical dimensions align. The ECNR50 is a Class RK5 fuse, which provides better protection for inductive loads like motors compared to fast-acting alternatives.

What is the difference between ECNR and FRN-R fuses?
While both are 250V Class RK5 fuses, ECNR is often used in Edison-branded or specific Cooper Bussmann series distribution. They are functionally interchangeable for most HVACR applications requiring time-delay protection.

Why is my ECNR50 still blowing during motor startup?
Ensure the fuse is sized to roughly 125% of the motor's running current. If it continues to blow, verify there is no single-phasing condition or mechanical binding in the motor or compressor.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.